The invention concerns an arrangement of seats for knives on a cutting shaft in a shredding machine according to one embodiment.
A known shredding machine is shown in FIG. 16 and disclosed in DE 42 42 740 A1 and can be used to shred and reduce wood, metal parts, plastic material, garbage and other waste materials.
The shredder 101 essentially consists of a material hopper 102, a feed unit 103 and a cutting tool 104. The three machine components 102, 103, 104 are connected to one another so as to be detachable by flanged couplings and, when assembled, form a feeding chamber 105. In the feeding chamber 105, a cutting shaft 106 driven by an electromotor engages in the lower area opposite the feed unit 103. The cutting shaft 106 is octagonal or polygonal in shape and is equipped with a number of cutting tools 107. The cutting tools 107 are fastened to the cutting shaft 106 and spirally wound and distributed over the periphery and are engaged with a first cutting plate 108 and a second cutting plate being used as a scraping bar 109. The upper side of the first cutting plate 108 is simultaneously part of the floor of the feed chamber 105. A perforated screen 111 fastened to reinforcing rings 110 is provided below the cutting shaft 106. A collecting tray 112 is situated below the sieve 111, a worm conveyor 113 being connected to the lowest point of said collecting tray for removing the crushed or shredded material. FIG. 17 shows the cutting shaft 16 in a perspective of a partial view, as seen from the feed chamber 105. The cutting shaft 106 has a number of cutting tools 107 which are attached to the cutting shaft 106 in a thread-like manner. The cutting tools 107 sit in the recesses 129 made in the cutting shaft 106. The recesses 129 extend from a first edge 140 of the cutting shaft 106 to the second edge 141 following in direction of rotation. The base 142 of the recess 129 deepens uniformly relative to a cutting shaft surface 139 over its entire longitudinal extension. The base 142 or the supporting area 131 forms a right angle with the contact surface 130. The height of the contact surface 130 between the second edge 141 and the base 142 corresponds to the diagonal extension of a cutting tool 107.
A known shredding machine of this type is also shown in the brochure xe2x80x9cHolzmag Zerkleinerungstechnikxe2x80x9d [Holzmag Shredding Technology] of Holzmag AG. In particular, a polygonal rotor shaft is shown which has knife seats and cutting tools inserted into the knife seats. The cutting tools are blocks rhombic in cross-section which are arranged in essentially V-shaped grooves which are distributed about the periphery of the shaft. The grooves are made in the shaft with bevelled cutters, which is why the end of the groove found in the shaft has a semicircular shape. The cutting tools, which have a flat rhombic front surface and a flat rhombic back surface, require a flat emplacement on the back of the knives in order to ensure an impact resistant fit in the grooves. To this end, semicircular positioning elements are inserted into the semicircular or semicylindrical groove ends and welded with the material of the shaft.
A shredding machine of this type has proven successful.
In the field of waste recyling and disposal of waste materials, disposal firms must respond more and more flexibly to the various materials to be processed. Thus, for example, not only hard materials such as plastic housings, plastic products, electronic parts or other breakable materials have to be crushed but also stretch materials, woven synthetic materials, carpets, threads and fibers of all types. In addition, the material to be cut can vary considerably in size and volume; for example, small-sized hollow plastic bodies (PET bottles) and plastic barrels must be handled. Experience has shown that unsatisfactory results are obtained with respect to the cutting operation when using a preset driving power or the cutting shaft and a preset size for the cutting tools.
The object of the invention is to create an arrangement of seats for knives on a cutting shaft with which different demands with respect to the cutting operation of the cutting shaft can be easily met.
According to the invention, the groove for the knife seat is designed in a such a way that knife positioning elements can be loosely inserted in the rear end area of the groove and are loosely mounted. The knife positioning elements or stop elements are kept radially covered by the cutting tool screwed into the knife seat and, in addition, centered by the back of the cutting tool.
The positioning surface or the positioning element can have a contour protruding beyond the shaft, which is preferably adapted to the contour of the knife, so that the knife is supported by the positioning element over the entire rear surface of the knife.
The knife positioning elements according to the invention are, like the knives, easily and quickly exchangeable, so that they can be exchanged for other knives having knife positioning elements adapted accordingly. In addition, it is advantageous that, when there is a damaging impact stress on the knife which e.g. leads to a deformation of the knife seat, the knife positioning element can be exchanged because it is merely inserted in a corresponding recess of the shaft and is not welded with the shaft. As a result, the energy expended when changing the knife position is considerably reduced.
According to the invention, a cutting shaft can also be equipped in such a way that, at a preset maximum driving power, it can be optimally designed for the material to be shredded.
According to the invention, at a constant driving power, a cutting shaft can be adjusted to the material to be shredded in such a way that cutting tools can be removed at certain points from the cutting tools that are spirally wound and distributed on the periphery of the cutting shaft and replaced by cover elements of the invention which cover the knife seat in a lid-like manner. This enables a reduction or increase of the number of tools at a constant driving power of the cutting shaft, i.e. the torque of the cutting shaft is distributed to different numbers of knives and thus adapted to the material to be chopped. With difficult-to-shred materials, as e.g. carpets or woven plastics, the force on the individual cutting tools can be appropriately increased by reducing the tools, whereby the cover elements of the invention ensure that no chopped materials accumulate in the knife seats and contaminate the knife seats or that thread-like material to be chopped winds about the shaft in the area of the empty knife seats without being cut. With hard materials to be cut, the cover elements ensure that the grooves for the knife seats are not damaged.
The invention shall be described in the following by way of example and with reference to drawings.